1. Field of the Invention
This invention relates to hydraulic accumulators adapted for use with gyratory crushers of the type in which hydraulic means is used to support the mainshaft on which the crushing head is mounted or otherwise supported, although the hydraulic accumulator of the invention is not necessarily restricted to such use; and the invention also relates to the combination of such hydraulic accumulator with a gyratory crusher.
2. Description of the Prior Art
It is well known in the prior art relating to gyratory crushers of the type using hydraulic means for supporting the mainshaft on which the crushing head is attached or otherwise supported to provide means for lowering the crushing head and the supporting shaft thereof when uncrushable material such as "tramp iron" enters the crushing chamber, whereby to permit the crusher to pass the tramp iron. "Tramp iron" is the term used in the art to designate an uncrushable object such as a metal dipper tooth or the like, for example, which is foreign to the mineral ore being processed by the crusher. The tramp iron relief is provided by conducting the hydraulic liquid beneath the piston which supports the crusher mainshaft to a hydraulic accumulator whereby the mainshaft and the crushing head supported thereby are lowered to permit passage of the tramp iron or the like through the crushing chamber. The hydraulic means for supporting the crusher shaft also permits lowering of the crusher shaft when other abnormal operating conditions are encountered, whereby to prevent breakage of the crusher parts. Examples of prior art patents showing the use of hydraulic accumulators for the purpose just mentioned in connection with gyratory crushers are U.S. Pat. No. 2,579,516 issued to Alexander J. Roubal on Dec. 25, 1951, and U.S. Pat. No. 2,667,309 issued to George D. Becker on Jan. 26, 1954.
Upon the presence of uncrushable material such as tramp iron in the crushing chamber of the gyratory chusher, during one gyration of the mainshaft to which the crushing head is attached or by which the crushing head is supported, 50 percent of the time the crushing head is closing on the tramp iron, forcing hydraulic fluid such as oil into the accumulator, and the other 50 percent of the time the crushing head is moving away from the tramp iron, and the accumulator is attempting to force the oil back to the cylinder in which the support piston which underlies the mainshaft is positioned.
Since the time period for one gyration of the mainshaft in a gyratory or cone crusher is a fraction of a second, the hydraulic oil must change directions rapidly. It is not possible for the oil to make a complete round trip from the cylinder for the support piston to the hydraulic accumulator and back to the cylinder in the very short time period of one gyration. Therefore, in the absence of a check valve in the hydraulic conduit connecting the crusher hydraulic cylinder to the accumulator, the oil going from the cylinder to the accumulator meets the oil going from the accumulator to the cylinder "head on." When this happens, "water hammer" occurs. The water hammer will build up in severity through each successive cycle of gyration until the connecting conduit from the cylinder to the accumulator breaks.
To prevent water hammer in a situation such as that just described, it has been the prior art practice to place a check valve in the hydraulic conduit connecting the accumulator to the cylinder for the support piston, this check valve being so constructed as to permit free flow of hydraulic oil from the crusher hydraulic cylinder to the accumulator but to provide a retarding action on the flow of the oil from the accumulator back to the cylinder. With each successive gyration, the crushing head hits the tramp iron and more oil is forced into the accumulator until the crushing chamber is opened far enough to pass the tramp iron. Upon clearance of the tramp iron through the crushing chamber, the oil is forced back to the cylinder for the support piston by the accumulator, setting the crushing head in its normal operating position. A check valve of the type just described connected in the hydraulic conduit from the accumulator to the cylinder for the support piston and permitting free flow of oil from the cylinder to the accumulator but retarding flow of oil from the accumulator back to the cylinder is diagrammatically shown as item 25 in the aforementioned U.S. Pat. No. 2,579,516 issued to Alexander J. Roubal. The use of a separate check valve such as the check valve 25 shown in the aforementioned U.S. Pat. No. 2,579,516, and the associated pipe fittings are relatively expensive.